<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width">
    <title>Document</title>
    <style>
        div {
            margin-top: 10px;
            ;
        }

        .box1 {
            width: 500px;
            height: 100px;
            border: 1px solid black;
            padding: 10px 20px;
            border-top-left-radius: 20px;
            border-bottom-right-radius: 20px;
        }

        .box2 {
            width: 300px;
            height: 50px;
            border-top: 1px solid red;
            border-bottom: 1px solid red;
        }

        .box3 {
            width: 10px;
            height: 10px;
            border: 3px solid green;
            border-radius: 50%;
        }

        .box4 {
            width: 100px;
            height: 50px;
            border: 5px dotted purple;
        }

        .box5 {
            width: 100px;
            height: 50px;
            border: 5px dashed purple;
        }
    </style>
</head>

<body>
    <div class="box1">you 四条边框</div>
    <div class="box2">you 两条边框 </div>
    <div class="box3">圆角边框</div>
    <div class="box4">点线</div>
    <div class="box5">虚线</div>